Tilting my head out from the cover of our longboat, I basked in the morning sun as we motored along the famous River Kwai. I ran the risk of being doused by the spray coming off the water, but I didn’t mind. It was just after 8:30 and, between the speed of our boat and the coolness of the air, it was the first time in Thailand that I’d felt even slightly chilled. Knowing it wouldn’t last, I savored the feeling as I surveyed the landscape around me.
We’d traded cropland for rolling hills and modest mountains. Everything was forested, from the riverbanks to the hilltops. Even in the dry season, the land was teeming with life, and we caught glimpses of Asian green bee-eaters (Merops orientalis), among other colorful birds, flitting from tree to tree along the shore.
I was seated behind Pongsanant, one of our Thai guides. At one point he turned to me and said, “This is my favorite part of the trip.” It was easy to see why. It was our first of only two full days in Kanchanaburi. Little did I know, those two days would become one of my favorite parts too.
Our destination that morning was a small cave set back from the river, nigh impossible to find without being guided to it. We passed through rubber farms, scaled slippery slopes, and some of the more venturesome members of our group (including Merlin!) waded through chest-deep water at a stream crossing. It made for a grand adventure – our most rugged by far.
During our time in Kanchanaburi, we were lucky to be joined by Surapon Duangkhae, MTBC’s Thailand Representative for Bat Conservation and Merlin’s former field assistant from over 40 years ago. Surapon studied the ecology and behavior of Kitti’s hog-nosed bats (Craseonycteris thonglongyai) in Western Thailand, research that led to the discovery of many of the caves in the area, including some of those we visited. His surveys determined that Kitti’s hog-nosed bats favor caves with certain characteristics, such as conical ceilings1. It was a privilege to have him join us: he was generous with his time and his knowledge, and he even briefly resumed his field duties to assist Merlin when crossing the river.
Part of our journey took us through orchards cultivating several fruits, including durian, which is heavily reliant on bats for pollination. Thailand is the largest exporter of durian worldwide which makes the protection of its pollinators crucial. As Merlin showed the group how to recognize which durian flowers had been visited by bats, I was struck by the extent to which entire livelihoods and international markets rely on these simple ecological interactions.
When we arrived at the cave, our efforts were rewarded with our first look at Kitti’s hog-nosed bats, one of a few species vying for the title of the world’s smallest mammal. When Daniel brought two out from the cave to show us, I couldn’t believe how easily the pair fit within the palm of his hand – with room to spare!
With the help of guides from nearby Sai Yok National Park, soon Melissa Donnelly and Danielle Cordani were busily showing the amazing variation found in Thai bats. These included a Great roundleaf bat (Hipposideros armiger) and a Thomas’s horseshoe bat (Rhinolophus thomasi) along with the Kitti’s hog-nosed bats from earlier. They demonstrated the differences between the species, pointing out contrasting body sizes and wing shapes, and highlighting the intricate nose-leafs on the horseshoe bats. When we moved on to other caves and captured other nose-leaf bats, we would be reminded of these characteristics for comparison between species.
Meanwhile, we took turns heading into the cave in smaller groups of three to four to minimize disturbance. The cave mouth was narrow: barely wide enough for Daniel to stand in with his arms outstretched. Not being the biggest fan of caves myself, I’ll admit I felt my chest tighten with apprehension. Whatever inborn trait it is that makes people like Merlin and Daniel feel at home in dark caverns, I don’t possess it. Armed with my headlamp and my wavering resolve, I followed Daniel as he turned and led us into the dark.
The cave sloped downwards for the first few meters before requiring us to get on our hands and knees and crawl through a low passageway into the main chambers beyond. Not every cave on our adventure would demand such acrobatics but I have no doubt that overcoming my fear in those tight spaces was worth it. It granted me the opportunity to see cave-dwelling bats in their natural habitat, clinging to walls or fluttering overhead, illuminated by the red beam from Daniel’s headlamp. Despite my nerves, every tentative step further from daylight gave me a greater appreciation for the unfamiliar world I found myself in.
Past the narrow passageway, the cave consisted of three chambers. We explored for a few minutes and caught sight of a handful of bats. Daniel pointed out the feathery remains of a small bird eaten by a Greater false vampire bat (Lyroderma lyra) and a lone whip scorpion creeping along the cave wall. I kept a lid on my anxiety long enough to shimmy back towards the main entrance and see daylight again. Pushing one’s comfort zone was all well and good, but perhaps also something best done in moderation.
Shortly afterward, our adventure on the River Kwai continued as we left the small cave behind. We retraced our steps through the jungle and rubber farms, stopping for coconuts and pomelos provided by farmers on our way. Eventually, we climbed back into our boats and sped along the river, returning to where we’d started before taking a break for lunch. Soon we were off again, headed for another cave.
That first cave was the most secluded of the ones we would visit in Kanchanaburi. The five others were more easily accessible and often home to Buddhist shrines. Over the next two days, we would encounter a long list of cave-dwelling bats including Lesser false vampire bats (Megaderma spasma), black-bearded tomb bats (Taphozous melanopogon), and Sunda short-nosed fruit bats (Cynopterus brachyotis). These small creatures inhabited a world completely foreign to me, but with each descent into the dark, I began to experience its appeal. The air held a rich, earthy smell, and the darkness was unexpectedly peaceful. There was a kind of silence underground that I hadn’t experienced anywhere else: a muted and heavy silence that demanded deference, something that noise-canceling headphones could never reproduce.
Like the earlier flying foxes, these bats were relatively tame, apparently accustomed to the monks’ protection. Flying bats would maneuver confidently around me, never once touching me. I was so at ease that I often closed my eyes. For several seconds, I would feel like I was a part of their world. My earlier fears forgotten, I couldn’t have been more grateful for the privilege.
An experienced park ranger named Sombat played an instrumental role in these extraordinary experiences. At each cave, he and/or Daniel would carefully venture into raised alcoves and narrow crevices, capturing isolated bats with butterfly nets. A few minutes later, they would return with bats for the MTBC team to show us.
In one cave, I decided I’d gotten comfortable enough to climb into one such alcove. Forced to crouch between the raised floor and the low ceiling, I could see diverging tunnels leading in all directions. Sombat climbed up after me and pointed enthusiastically to a passageway that descended downward in front of us. I shook my head at him. We didn’t need a common language to convey our respective feelings. He grinned at me before climbing nimbly into a narrow hole that wouldn’t have been wide enough to pirouette in. The light of his headlamp dwindled as he crawled into whatever cavern lay below. I waited with bated breath to see what he’d find. A Kitti’s hog-nosed bat whirled past, and a few moments later Sombat emerged, his hand held above him, a tiny bat in his grasp.
Seeing Kitti’s hog-nosed bats was one of the highlights of the trip, surpassed only by having the opportunity to hold one. During one of our cave visits, Daniel carefully transferred one of the small bats to my open hand. Kitti’s hog-nosed bats, also called ‘bumblebee bats’, typically weigh about 2 grams (0.071 oz), roughly the same weight as a U.S. penny. Against my gloved hand, it almost felt like I held nothing at all.
While I was absorbed with my new, tiny friend, Daniel retrieved a Lego minifigure to use for scale in some photos. I couldn’t help but laugh as he placed the toy next to the bat in my palm. The incredible diversity of bats is something that has always fascinated me. Two days ago, we’d been watching giants fly overhead. Today, I held one of the world’s smallest mammals in the palm of my hand. What would tomorrow bring?
References
1. Duangkhae, Surapon. “Search for Kitti’s Hog-Nosed Bat Craeseonycteris Thonglongyai in Western Thailand.” Nat. Hist. Bull. Siam Soc. 39 (1991): 1–17.